Method of producing bimetallic printing forms



Feb. 5, 1952 2,584,317

METHOD OF PRODUCING BIMETALLIC PRINTING FORMS c. B., ALLER 7 w i MWMINVENTOR CLAES BQRGE ALLER ATTORNEY Patented Feb. 5, 1952 time on.

2,584,317 z. .i 6D'Uoi'NG-BiME'rALLIc orrice e Binge l a. e ea rkAttract-m December 29, 1947; SeiialNo. 794L257 Section- 1; Public Law690,- Aii'gu'st 8; l946 Patent expires Septemberd), 1966 ;Thepresentinvention;relates to a method of producingbimetallic printingforms,.i. e printing forms in which theparts of the printing surfacewhich areito transfer ink during printingha're madegof another metalthan the, parts that are. 5 not-required to transfer;ink;.i Bimetallicprinting forms; are. mostly used for :planographic printing;particularly offset, the twometals being soichosen that:;in presence or:water; one a; will retain ;the water ;andi;repel;ink whereas :the etherzone in 10 spite-of the. presenceiof water. will retain-printers inkand:thus.;transfer ink'in the printing process;

In asuch; planographic printing processes the height of theink-retaining partsimay difierifrom; that-mi zthe' ink-repelling: parts.of:;.the :printing plate, butin most cases :there is either -no"difier=ence;in: height or the differenceisiso: small that. iUfiS. ofz'norsignificancexior printing purposes;- The .;present invention; more"particularly: relates" t the production of printing plates of the latterkind; .15.; 1:.1'. 19.. J in L In the production of such;planographicllprinte; ing' platesit. is known to :deposit on the"surface of; the metal which is. totforml onerof the; surfacecomponents-in "the/printing process'ia continuous layer pf the-g'metalz.which is; .to; form; therother surface: component;;after;:which' 'acopyinglayer; isgappliedto the surface of the-metallic layer lastmentioned; afterwhich copyingis carriedsout and. thegcopying layer isdeveloped, :andxthe parts of w thergmetallic intermediate. :layer which.are. not coyered: by thelzcopying layer .afterjdevelopment are etchedright through to the supporting layer." Inxprder tobetter protect theparts ofithe intermediatemeta-llic layer coveredbyxthe parts'of thevcopyremaining after development the lattermay be hardened'by being burntin. or by. melting inksuitable protecting}. agents. After etching saidprotecting, agents and the parts of the.copy ingJayernot, removed .indevelopment may be 4(} removed inknown manner; l V

This known method suffers from several draw backs; Thus it has beenfound thattherecan"-'f not be obtained in this manneratruerecording'fand a -s'uflicient protection of 'the' finer printing" 5 elements duringetching. This'is due*'to* the* etchingagent being to some extentcapableof penetrating "to the back of' 'the' protecting lay'e'r fro'mthe borders ofthe areas'prote'cted and thus s alter the: size or shapeofiithe sprinting: elements. o1t:,caus.e;them;to:adhereinsufiicientlyto. the sup- D 1122 11dipth syd achv themselves-.11.; a a .11; Itgisalsoknown to deposit the ink-retaining. metahcomponent through the openings01 2, copy produced directly on the surface of the other 2 Claims. (Cl.204-17) metal component. -In this process it has, how'- ever,- beendifficult to obtain adeposit of equal thickness vin smaller and greaterprinting areas.- Consequently in many-cases a correct recording ofthevalues oflhalftones cannot be obtained and=the printing=elements will insome places wean/too fast ordetachr 1;: r 1

q Moreover it z-has been proposed in 'a-method t which allegedly can: beusedin-connection with both :reliet intagl-io land planographic printingto :deep-etch-the supporting metal after areas-0f another metal,:fillingdnl metah have been de-. posited thereon through :the openingsof a copy asdescribed above, using for the said deepetchinganetchingagent which does-not attack thefilling-in metal. In ordertc-broaden the base part of the saidfilling-in metal to make it adherebetter to thesupporta layer-of resinis applied betweenwthe supportingand the copyinglayer and after-(development of the copy the resin isre=- moved within? the non-ecovered-areas the removal being-extended:slightly behind-"the covered areas too-in order to'allow-forthe saidbroadening of the bases .of. the: filling-in metal; This method,however; -is-not suited =forplanographic plates; since then-said basewill alter the value of the half f nes g l4, v .7 The; objectofleth-iswinventiont is a method-of producing planographic printingforms in which all these drawbacks are removed; Otherobjects andpurposeseof the inventionwihappear from thefollowingldescriptionandelaims. ,lBroadly therinvention consists a in a method: of producingplanographic printing forms in which approtecting imagea-is used forprotecting theparts of the printing surface oftheform which areIlOtetObe attacked by theetching agent duning'etchinge'and the-ieaturecharacterizing theinventiQnEis-thatvthe protecting image is applied toI, the.-;surface: -of aj ga-lvanicallydeposited continuous-intermediatelayer of a metal acting as one of themetalliccomponents in the plano---graphic printing aiprocess which intermediate metal layer -iis againplaced upon a base-layer' of- -a material acting as the other metalliccomponent inethe bimetallic-planographic; printing process :andthernone-protected parts of the metallic intermediate layer are-etched awayright a through to the surface of the base, metalsby an:

etching=agent which does not attacl; the protecting metal. 1 l-,1. ,7;(More particularly.according to the invention thee-methodis appliedtothe-production of print ingaforms in which one oi-thecomponentsenteringin the bimetallic printing process is chromium or a chromium-containingalloy or stainless steel.

Between the intermediate layer and the pro tecting metal and between theintermediate layer and the base metal which layers are both of metalsforming the components of a bimetallic planographic printing processthere may be interposed other metals for instance silver for otherpurposes such as for improving adhesion or facilitating good deposition.The claims are to be understood so as to comprise methods-in which thisis the case if for any purpose it should be desired.

In contradistinction to the known method in which a continuous metallayer deposited on a support of the metal which is to form one of thecomponents in a bimetallic printing process is protected during etchingby a copy, a metal is used according to the present invention for theprotection of the areas which are not to beattacked during etching,which has the effect that these parts will not at all be attacked.Consequently recording will be exact and the printing elements willnotalter their size or shape or adhere insufiiciently to the support.

The method which forms the subject matter of the presentinventionmoreover differs from the known method in which-the one metalliccomponent is deposited upon the other one through the openings of a copyplaced thereon in that none of the two metallic components in thebimetallic planographic printing process are according to the presentinvention deposited through the openings of the copy. Thereby it isavoided that the deposited metallic component of v the said process willappear in undesired unevenness of thickness.

From the known method which is also mentioned above in which the basemetal is deepetched after a metal hasbeen deposited on it through theopenings of a copy produced on the surface thereof the present methoddiifers not only in that no resin layeris interposedbetween the basemetal and the copy as mentioned above but also in that the metallicintermediate layer original copy. The exactness is due to the thinnessof the intermediate layer and the-capability of the protecting layer tocompletely protect the parts covered thereby. Such exactness will not beobtained in the known method even if etching is carried to such a depththat it reaches a further base plate supporting the firstone and beingof steel. This appears from the fact that the walls of the pits producedby etching are not vertical and that the purpose of the resinous layerused in the known method is to avoid the walls being vertical in orderto secure the partsremaining after etching a broader base.

The term etchable and non-etchable-used above and in the following isnotto be taken in the absolute sense of the word but means that themetalin question is one that is not attacked in the etching process inquestion.

In connection with using chromium, chromium-containing alloysorstainless steel as the water-retaining component which'is the mostimportant kind of planographic process with which the present inventioncan be used and particular great advantage can be obtained there may beused as is well known copper, brass or bronze as the ink-retainingcomponent. These components will act in the printing process in the saidcapacities irrespectively whether one or the other is placed in theuppermost position and the present invention can be employed inconnection with both possibilities. If chromium or a chromium-containingalloy is placed on a surface of an ink-retaining metal such as copper,

brass or bronze it is on the surface of the chromium etc. that theprotecting metal is to be placed and the chromium etc. must then beetched through at the same time leaving the protecting metal as anon-etchable metal. An example of an etching agent by means of whichthis can be carried into efiect is hydrochloric acid provided that theprotecting metal is one not attacked by this acid for instance lead. Ifon the other hand an ink-retaining metal such as copper, brass or bronzeis placed on the surface of the ink repelling metal, chromium,chromium-containing alloy or stainless steel the inkretaining metal mustnow be etchable and an etching agent capable of etching the exposedparts thereof away must be used. Examples of such etching agents aregiven in the following. Also in this case, however, the protecting metalmust be non-etchable to the etching agent used.

According to an embodiment of the invention iron, lead or tin or alloysthereof are used for the protecting metal. These metals. are easy toapply in the electrolytical way and they ofier an excelent protectionfor the parts of the metallic interlayer which are not to be removed.Also in this case there may be used an acid etching and if the metallicinterlayer is an ink-retaining component such as copper, brass orbronze, chromic acid is very suitable since it removes such metals veryreadily and does not attack the protecting metals even iron.

According to another embodiment of the invention not only iron, lead ortin but also many other metals may be used for the protecting metal suchas zinc or cadmium if for the etching agent there is used a sulphidizingagent such as a solution of an alkali metal sulphide or alkali metalpolysulphide, which converts the intermediate metal layer into an easilyremovable sulphide if this consists of copper, brass or bronze. If itconsists of chromium etc. evidently this etching cannot be used.

In case of extremely delicate printing elements this embodiment may beeven preferable to the acid-etching method mentioned above since it ispractically undamaging to such elements.

If a sulphidizing etching agent is used it is preferable to support theetching process by using an electric current, which is passed throughthe etching agent using the printing form as one of the electrodes inthe circuit. To remove the sulphide formed by the etching process itmay.

be necessary to employ a powerful rinsing or a slight rubbing. action.

Generally the protecting metal is to be removed from the surface of theintermediate layer of metal before printing. This can be done'by meansof an acid etching agent which does not' attack either of the two metalsentering into the planographic printing process. In most cases dilutedsulphuricacid will be found suitable.

The deposition of the protecting metal is preferably carried out bymeans of the electric current.

Two embodiments of the invention will be described in the following withreference to the drawing in which Figs. 1-4 show schematically thevarious layers of a printing form in section on four stages of itsproduction.

Example 1 A plate S of stainless steel or of copper or nickel coated onone side with chromium or any other plate of which at least one surfaceis a surface of chromium or chromium-containing alloys, for instance,stainless steel is covered on the surface consisting of chromium,chromiumcontaining alloy or stainless steel with a continuous layer ofcopper C. To the layer of copper there is applied a light sensitivefilm, for example, a chromate-gelatine layer which is then exposed tothe influence of light through a transparent positive and developed inthe ordinary manner. The parts of the copying layer remaining afterdevelopment on the surface of the continuous layer of copper isdesignated by L in Fig. 1.

The printing form appears now as a chromatecolloid image on a base ofcopper. This image is negative when considered as an image of colloidand positive if it is considered as an image of uncovered coppersurfaces.

In order to protect the copper surface elements during the removal ofthe areas now covered by colloid a protecting metal F is applied to thesaid areas. The protecting consists in iron which is deposited in theelectrolytical way.

For this purpose an aqueous solution of an iron salt is applied to thesurface of the plate placed on a table by means of a brush in the bottomof which at the roots of the bristles an iron electrode connectedthrough the handle to the positive pole of a source of electricity isplaced. At the same time the printing form is connected to the negativepole. By working on the plate with such a brush a layer of iron is inall parts of sufiicient thickness can be deposited in all openings ofthe layer of colloid even the tiniest.

Then the colloid image is removed by hot water and the plate is nowcomposed as shown in Fig. 2.

Now the copper is removed by etching from the areas which are notcovered with iron. The etching agent consists of chromic acid made bydissolving chromic, acid anhydride in water. The plate is now composedas shown in Fig. 3.

After this the layer of iron is removed by means of an etching agentconsisting of a solution of diluted sulphuric acid or nitric acid afterwhich the plate composed as shown in Fig. 4 is ready of use.

In the drawing the layer of copper and the layer of protecting metal isshown in exaggerated thickness. In fact the layer of copper must be asthin as possible. Theoretically it needs only be of molecular thickness,but to increase its resistance to wear its thickness may practically beincreased to, for example, a few hundredths of a millimeter. Theprotecting metal may be used in similar thickness.

Example 2 .The plate S is of copper or steel coated on at least one sidewith a layer of copper. This plate is now covered on the copper surfacewith a con- 6 tinuous layer of chromium C, for instance, byelectrodeposition. As to the thickness of the layer or chromium the sameconsiderations apply as in the case of copper in Example 1. copyinglayer is applied in the same manner as in Example 1 and exposed througha negative.

The printing form snows now a colloid image on a base of chromium. Theimage is positive when considered as a colloid image and negative ifconsidered as an image of uncovered chromium surface elements.

In order to protect the chromium surface areas to be maintained duringetching of the areas to be removed a protecting metal F consisting oflead is deposited on the surface areas not covered by the colloid image.The lead is deposited by electrolysis in the manner described in Examplel. The colloid image is removed and the plate will be of theconstruction shown in Fig. 2.

Then the chromium is removed from the areas not covered by lead 101'which purpose the etching agent consists of hydrochloric acid which willnot attack the lead and copper. The plate is now constructed as shown inFig. 3.

Finally the layer of lead is removed by means of nitric acid arter whichthe plate shown in Fig. 4 will be ready for use.

I claim:

1. lvletllod of producing a planographic printing form withbhnetallicsuriace comprising the steps of: depositing gaivanically on toa base of stainless steel a thin continuous layer of copper, applying tothis galvamcally deposited layer an image forming coating covering suchparts of the layer subsequently to be removed, galvanically depositingon uncovered parts of the copper layer a thin layer or iron, removingthe image Iorming coating, removing uncovered copper down to the baselayer by means of cnromic acid and removing the iron layer by dilutesulphuric acid.

2. Method of produclng a planographic printing form with bimetallicsurface comprising applying to the copper layer of a bimetallic printingform consisting of a stainless steel base carrymg a thin continuouslayer of copper. an image forming coating covering such parts of thecopper layer which are subsequently to be removed, depositinggalvanically on the uncovered parts of the copper layer a thin layer ofiron, removing the image forming coating, removing uncovered copper downto the base layer by means of chromic acid, and then removing the ironresist.

CLAES BQRGE ALLER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 444,951 Goodwin Jan. 20, 1891758,599 Sachers Apr. 26, 1904 797,668 De ey Aug. 22, 1905 1,376,365Wertheimer Apr. 26, 1921 1,783,664 McFarland Dec. 2, 1930 1,871,734Trist June 23, 1931 1,886,817 Johnston Nov. 8, 1932 2,214,950 AllerSept. 17, 1940 2,241,585 Day May 13, 1941 2,408,220 Lum Sept. 24, 1946The

1. METHOD OF PRODUCING A PLANOGRAPHIC PRINTING FORM WITH BIMETALLICSURFACE COMPRISING THE STEPS OF: DEPOSITING GALVANICALLY ON TO A BASE OFSTAINLESS STEEL A THIN CONTINUOUS LAYER OF COPPER, APPLYING TO THISGALVANICALLY DEPOSITED LAYER AN IMAGE FORMING COATING COVERING SUCHPARTS OF THE LAYER SUBSEQUENTLY TO BE REMOVED, GALVANICALLY DEPOSITINGON UNCOVERED PARTS OF THE COPPER LAYER A THIN LAYER OF IRON, REMOVINGTHE IMAGE FORMING COATING, REMOVING UNCOVERED COPPER DOWN TO THE BASELAYER BY MEANS OF CHROMIC ACID AND REMOVING THE IRON LAYER BY DILUTESULPHURIC ACID.